Ring expander



Patented June 9, 1942 UNITED sT TES PATE T OFFICE RING EXPANDER Donald H. Pratt, Bangor, Maine; Glenna Pratt administratrix of said Donald H. Pratt,

deceased 1 Claim.

'Ihis invention relates to ring expanders and has for an object the provision of an improved device cf this character. More particularly, the invention aims to provide a ring expander comprising a conical segmental expander which is circular in cross-section when in its contracted position and means for moving the segments of the expander outwardly and inwardly in a succession of operations to expand the ring in successive small increments. The expander of the invention is constructed and arranged to expand the ring in a succession of separate expansions during which the ring is not appreciably changed from a true circle.

The segmental expander has a conical central the segments radially as they are moved outwardly and inwardly under the action of the conical mandrel. The mandrel is preferably reciprocated by a cam actuated ram attached to any suitable hand operated means such as a lever. tageously constructed to be mounted upon a bench or table and the cam is oscillated to any desired degree consistent with the amount of expansion desired for each increment of expansion. Each time the hand lever is moved through a short arc and returned to its starting position the segmental member is expanded and returned to its circular contracted position.

In the accompanying drawing:

Fig. 1 is a cross-sectional side view, with parts shown in elevation, of a ring expander embodying the invention;

Fig. 2 is a cross-sectional end view, with parts shown in elevation, of the ring expander of Fig. 1;

Fig. 3 is a view along the line 3 3 of Fig. 1 with the segmental elements shown in contracted position;

Fig. 4 is a view similar to Fig. 3 with the` segmental elements .shown in expanded position; and

Fig. 5 is a view along the line of Fig. 1.

The ring expander illustrated in the accompanying drawing comprises a casing l having a vertical cylindrical bore 2 intersected by a horizontal cylindrical bore 3 and a flared base having holes :i for securing the device to a bench or the like. Concentric with and above the The device of the invention is advancylindrical bore 2 is a shoulder 6 having a central opening.

A shaft 1 is secured in rotatable position within the bore 3 by an end plate 8. One end of the shaft extends beyond the coverV to which is attached a hand lever 9, and the other end has an eccentric smaller diameter portion l0 projecting into the bore 2 over which is mounted a cam roller H. The shaft extension I0 and cam roller Il extend suhiciently into the cylindrical bore 2 to engage a slot I2 in the ram I3 which is reciprocably mounted in the bore 2. A conically formed mandrel l5 is screwed into the upper end of the ram and passes concentrally through the central opening of the shoulder 6. The upper portion I6 of the casing extends beyond the shoulder 6 forming a central opening Il'.

The conical segmental expander 2li, as shown in the drawing, comprises four segmental parts and when these parts are in contracted position, as shown in Fig. 3, the inner and outer surfaces are circular. This member is preferably formed by radially slitting a piece of steel or similar material having a conical exterior and interior into four longitudinal segments. When these segmental members are assembled, they are not circular in cross section, either inside or outside, and in order to make them circular, they are fastened together and machined inside and outside to perfect circles. The lower end portion of the segmental expander has an annular shoulder 25, a cylindrical portion 2t over which is mounted a coil spring 2l, and a cylindrical portion 2B. The cylindrical portion 23 is slightly smaller than the opening in the shoulder 6 but the cylindrical portion 26 is slightly larger, thereby providing a shoulder 29 to serve as a base for the segmental expander and limit its downward motion. The upper end I6 of the casing is provided with a cover 30 secured in place by the screws 3E. The cover has a central opening 32 of suflicient internal diameter to permit the expander 20 to expand, and to overhang the annular extension 25 and secure the member 20 in position, preventing it from moving upwardly. Each of the segmental parts of the expander 20 is provided with a lug 35 arranged to effect a sliding engagement with one of the longitudinal grooves 36 in the mandrel i5. The upper end portion of the expander is recessed to accommodate a coil spring 3l. The springs 2l and 31 are similarly constructed helical springs which are forced under tension into their respective positions, These springs hold the segments of the expander in snug engagement with the mandrel and return the segments to their contracted positions when the mandrel is moved downwardly.

The expander of the invention is suitably secured as by means of bolts to a table or bench (not shown) and the ring to be expanded is slipped over the segmental expander 20 and forced downwardly by hand until it reaches a position where it makes snug engagement. The lever 9 is given a small oscillatory movement causing the eccentric roller or cam Il to force the ram upwardly, thereby forcing the mandrel I5 into expanding engagement with the segmental expander 20 forcing the various vsegments thereof outward radially. The outward radial movement of the segments is assured by the sliding guided movement of the lugs 35 in the grooves 36. Even the maximum movement of the lever 9 only expands the segmental expander 20 a relatively small amount, thereby enlarging the ring by a relatively small increment. The lever is returned to its original position, thereby drawing the mandrel downwardly and the springs 21 and 31 return the segments of the expander to the contracted position. By applying hand pressure to the ring forcing it downward to a new position, the lever may again be moved to the position of maximum expansion or to any intermediary position depending upon the increment of expansion considered necessary for each particular operation.

The ring expander of the invention is constructed and arranged to permit only a relatively small expansion of the ring for each position the ring may occupy on the segmental expander. As a consequence, the ring cannot be excessively expanded at any position on the segmental expander. It is clear that as the segments of the segmental expander are forced outwardly, the exterior becomes non-circular but since this movement is relatively small, even at the maximum, the segmental expander does not appreciably change from a true circle. The ring expander of the invention expands the ring in a succession of small increments during which time the segmental expander does not appreciably change from a true circle.

I claim:

A finger ring expander which comprises a relatively long conical segmental expander having a gradual taper and formed of a plurality of radially disposed segments having a central longitudinal opening, the segmental expander being circular in cross-section when the segments are together in contracted position, a conical mandrel reciprocable in the opening for moving the segments into an expanded position, spring means for returning the segments to their contracted position, a lug attached to and projecting inwardly from each segment and a separate groove in the mandrel for engaging one lug to guide the segments radially as they move to the expanded position and to the contracted position, said conical mandrel being reciprocable in the opening and being constructed and arranged to move the segmental members only a relatively small amount during each expansion, the segmental expander not appreciably changing from a true circle even at maximum expansion, whereby the ring to be expanded may be subjected to a series of small increments of expansion without appreciable circular deformation.

DONALD H. PRATT. 

